1. Field of the Invention
This invention relates to a process for the activation and/or regeneration of supported noble metal catalysts used for fluorohalocarbon or fluorohalohydrocarbon hydrodechlorination.
2. Background
Many factors are involved in the deactivation of a catalyst. Some causes of deactivation include: sintering, poisoning of active sites, physical deterioration such as crumbling, and coking. The exact cause of catalyst activity degeneration and its effects on a process depend on the nature of the process.
The regeneration of the activity of reforming catalysts has been studied for many years. Elaborate and costly procedures are typically required to restore catalyst activity. For example, J. P. Franck and G. Martino in "Progress in Catalyst Deactivation," ed. by J. L. Figueiredo, Martinus Nijhoff, The Hague, 1982, p. 386 ff, describe a normal regeneration procedure for reforming catalysts which involves four stages. The first stage usually involves cooling the catalyst to some lower than operating temperature (about 200.degree. C.), followed by removal of hydrocarbons and hydrogen by nitrogen. The second stage involves elimination of coke by combustion at 380.degree. to about 500.degree. C. During this stage it may be necessary to inject HCl, CCl.sub.4, 1,2-dichloropropane or any other halogenated hydrocarbon which will produce HCl, during the combustion phase. The third stage involves restoration of catalyst acidity by increasing its chlorine content, in the form of HCl or a chlorinated compound such as CCl.sub.4, to the desired level at about 500.degree. C. in the presence of air. The last stage usually involves treating the catalyst with chlorine and oxygen at about 510.degree.-530.degree. C. in order to redisperse the platinum crystallites.
It is seen that there is a need for a simple and effective regeneration procedure.
Jap. Pat. Appln. 62-282645 (CA:109:54312r) discloses a process for the regeneration of supported palladium catalysts used for the hydrogenation of dienes by rinsing the used catalyst with aromatic hydrocarbons. The hydrocarbon treated catalysts were more effective than control catalysts treated with acetone.
Jap. Pat. Appln. 59-196742 (CA:102:68105t) discloses the regeneration of a palladium-containing catalyst, used for the purification of olefins by hydrogenation, by washing the spent catalyst with sulfur-free unsaturated or saturated hydrocarbons.
Jap. Pat. Appln. 54-87693 (CA:92:22019q) discloses the regeneration of various supported metal catalysts, including palladium, used for the purification of olefins by hydrogenation, by washing the spent catalyst with a C.sub.2 -C.sub.12 olefin and/or paraffin, containing no aromatic hydrocarbon, at -30.degree. to 170.degree. C. and 0-100 kg/cm.sup.2 gauge.
U.S. Pat. No. 4,164,481 discloses a process for the regeneration of Pd/C catalysts used for the hydrogenation of p-nitrophenol to p-aminophenol. The catalysts are regenerated by washing the deactivated catalysts with a polar organic solvent, e.g. acetic acid, contacting the washed catalyst with a hot aqueous alkali metal hydroxide solution, contacting the catalyst with an O-containing gas at moderately elevated temperatures, and washing the catalyst a final time with polar organic solvent.
Ger. Offen. DE 2,009,114 (CA:75:133480b) discloses a process for the regeneration of spent Pd catalysts from hydrogenation or hydrogenolysis processes. The deactivated catalysts are suspended in a solvent, e.g. CHCl.sub.3 or CH.sub.2 Cl.sub.2 and treated with chlorine, optionally together with nitrogen, followed by drying to obtain an active catalyst.